1. Field of Invention
The present invention relates to a device for measuring the weight of a vehicle seat including the weight of a person sitting on the vehicle seat. In particular, the present invention relates to a seat weight measuring device which is improved such that the performance of a load sensor is not impaired by dimensional errors, deformation, etc. of the vehicle body and seats.
2. Description of the Related Art
An automobile is equipped with various devices for securing the safety of the driver and passengers, such as seat belts and air bags. The recent trend for further improving the performance of the seat belts and air bags is to control the operation of these safety devices according to the weight (body weight) of the person. For example, the development gas amount and development speed of the air bags are adjusted and the pretension of the seat belt is adjusted in accordance with the weight of the person. For this purpose, it is necessary to determine the weight of the person sitting on the seat. A device for determining a person""s weight has been developed. The device includes load sensors (load cells) arranged in the four corners under the seat. The sum total of the vertical loads applied to the load cells is obtained, thereby allowing the seat weight including the weight of the person to be determined (Japanese Patent Applications No. 9-156666, 10-121627, etc. filed by the same applicant).
According to the present invention a seat weight measuring device for measuring the weight of a vehicle seat including the weight of a person sitting on it is provided. The device includes a load sensor inserted into the seat or between the seat and a vehicle body and adapted to convert at least a part of the seat weight to an electric signal, and an absorption mechanism for absorbing deviation and/or deflection between the seat and the vehicle body. The absorption mechanism is slidable by LIR at the maximum from side to side. The distance LIR may be defined as follow:
LIR=(a+bxcex4)xc3x97xcex3/(xcex1+xcex3)+(cxcex4/2)xc3x97xcex3/(xcex2+xcex3)
where
a: dimensional tolerance (mm) of the center with respect to the fore-and-aft direction of right and left seat rails when securing the seat rails to the vehicle body;
b: maximum stroke (mm) that seat slides are capable of sliding;
c: distance between fixed points (load sensor center positions) in front of and behind the seat rails;
xcex4: sine value (sin xcex8) of the tolerance xcex8 of the relative angle deviation of the right and left seat rails when securing the seat rails to the vehicle body;
xcex1: deflection amount (mm/kgf) per unit load when causing a lateral deformation (opening and closing) between the right and left seat slides;
xcex2: deflection amount (mm/kgf) per unit load when twisting the right and left seat slides laterally and reversely in the longitudinal direction; and
xcex3: slide amount (mm/kgf) per unit load when sliding the absorption mechanism.
The present invention also includes a seat weight measuring device for measuring the weight of a vehicle seat including the weight of a person sitting on it, that includes a load sensor inserted into the seat or between the seat and a vehicle body and adapted to convert at least a part of the seat weight to an electric signal, and an absorption mechanism for absorbing deviation and/or deflection between the seat and the vehicle body.
The absorption mechanism may include a pin for connecting the vehicle seat to the vehicle body, the pin passing through a hole. The hole may be sized to provide a clearance about the pin to thereby allow vertical and longitudinal deviation between the vehicle seat and the vehicle body.
Where the vehicle seat includes seat rails attached to a supporting bracket, the absorption mechanism may also include an arm pivotally connected to the vehicle body and including a pair of side plates, the supporting bracket being positioned between the side plates so that a clearance between the bracket and the side plates is provided to thereby allow lateral deviation between the vehicle seat and the vehicle body.
The absorption mechanism may also include a plate spring positioned in the clearance between the bracket and the side plates to thereby center the bracket between the side rails.